Sleeve

ABSTRACT

The invention relates to a sleeve ( 1 ), for a bone fixation element, in particular, a wire ( 10 ), comprising A) two tubular elements ( 3; 4 ), having a common longitudinal axis ( 2 ), each with a central drilling ( 8 ) of the same diameter (D), an external end ( 20; 21 ) and an intermediate end ( 22; 23 ) with a front face ( 28; 29 ) and B) a shearable connector web ( 5 ), fixed to the two tubular elements ( 3; 4 ), outside the central drilling ( 8 ), by means of which the two tubular elements ( 3; 4 ) are axially connected to each other.

The invention relates to a sleeve which is mountable as the endprotection or head on a longitudinal bone fixation element, inparticular a cylindrical or hollow cylindrical wire, according to thepreamble of Patent Claim 1 and it relates to a device for fixation ofbones or bone fragments according to the preamble of Claim 15.

Kirschner wires, pins or Schanz screws are often used in surgery and fora wide variety of applications. Such thin wires or screws are firstattached to a bone or bone fragment at their distal end and thenattached to an external fixator in accordance with their function. Afterbeing attached to the bone, wires are cut to their desired length.Disadvantages of this technique include the fact that

-   -   after being cut, the free end of the wire has a burr which may        cause irritation to the adjacent soft tissue; and    -   use of such wires is limited by the fact that practically only        force-locking connections to other parts, e.g., screw heads or        other anchoring elements, may be used on the proximal end of the        wire. However this is unfavorable for applications as        compression screws.

DE 94 90 219 to HOWMEDICA discloses, for example, a compression devicecomprising a longitudinal bone fixation element with an axiallydisplaceable stopper that can be locked in the desired position. Theshaft and the central bore in the stopper each have a non-roundcross-sectional area, so that the stopper is also locked with regard torotation about the longitudinal axis of the bone fixation element. Onedisadvantage of this known device is that the bone fixation element mustbe designed like a toothed rack, which means a complex manufacturingprocess and thus high costs.

The present invention seeks to remedy this situation. The invention isbased on the object of creating a sleeve which has an aligned centralbore in the undeformed state and is defoimable by shearing across itslongitudinal axis without applying any great force, such that it has twoaxial segments that are joined together and have central bores that arenot aligned.

The present invention achieves the object as formulated with a sleevehaving the features of Claim 1 and a device for fixation of bones orbone fragments having the features of Claim 15.

Additional advantageous embodiments of the invention are characterizedin the dependent claims.

The advantages achieved through the invention can essentially beregarded as the fact that, thanks to the inventive sleeve,

-   -   the end of a severed wire can be designed to be free of any burr        by applying a sleeve. The edge formed by the severing operation        on the wire is covered by the sleeve; and    -   a sleeve can be attached in a form-fitting manner axially and        rotationally to a conventional commercial wire at any desired        location so that tensile forces or impact forces and/or torques        can be transmitted between the wire and the sleeve or another        part that is connectable to the sleeve.

In a preferred embodiment, the connecting web is arranged parallel tothe longitudinal axis between the front faces on the intermediate endsof the tubular elements, so that there are no parts on the sleeve thatprotrude beyond the periphery of the tubular elements and couldinterfere with the removal of the instrument used for fixation of thesleeve.

The connecting web preferably has a cross-sectional area that isorthogonal to the longitudinal axis and is within a circular ringsegment with a central angle α between 5° and 350°. The cross-sectionalarea of the connecting web is of such dimensions that the connecting webcan be sheared with a simple instrument that is operable by hand withoutapplying any great force. The fixation of the sleeve to the wire isaccomplished by shearing of the connecting web.

In another embodiment, the outer lateral surfaces of the tubularelements each have a planar surface parallel to the longitudinal axis,so that a twist-proof locking can be guaranteed.

In another embodiment, the sleeve is designed with a conical end facingthe tip of the wire and has a conical thread. Therefore, this yields theadvantages that

-   -   a wire designed with a thread at the tip, for example, may be        used as a bone screw together with a sleeve connectable to the        bone plate in a stable angle as the screw head; or    -   the thread on the sleeve can be screwed directly into a bone or        a bone fragment, so that the wire together with the sleeve may        be used as a compression screw.

In yet another embodiment, the sleeve is provided with a continuous borethat does not cut through the central bore, so that a wire or thread canbe secured on the sleeve and thus on the wire.

In one embodiment of the device, two sleeves are secured at the desiredmutual spacing on a wire. The distance between the sleeves in relationto one another is freely selectable. This yields the advantage that twoor more bone fragments can be secured between the sleeves. The ends ofthe sleeve directed toward the bone or the bone fragments may bedesigned as simple supports or may be provided with a thread.

The invention and further embodiments of the invention are described ingreater detail below on the basis of the partially schematic diagrams ofseveral exemplary embodiments.

FIG. 1 shows a perspective view of an embodiment of the inventivesleeve;

FIG. 2 shows a longitudinal section through the embodiment of theinventive sleeve shown in FIG. 1;

FIG. 3 shows a section along line II-II in FIG. 2;

FIG. 4 shows a longitudinal section through an embodiment of theinventive device prior to its fixation; and

FIG. 5 shows a longitudinal section through the embodiment of theinventive device shown in FIG. 3 in the fixated state.

FIGS. 1 through 3 illustrate an embodiment of a one-piece sleeve havingtwo tubular elements 3; 4 arranged in succession and coaxially with alongitudinal axis 2, said tubular elements being joined together in anaxially fixed relationship by means of a connecting web 5. The tubularelements 3; 4 each have an axially protruding end 20; 21, anintermediate end 22; 23 and a coaxial central bore 8. The two tubularelements 3; 4 are also designed as circular cylinders, where the lateralsurface 24 of the first tubular element 3 has a diameter D₁ and thelateral surface 25 of the second tubular element 4 has a diameter D₂.The difference between the diameter D₁ of the first tubular element andthe diameter D₂ of the second tubular element is such that this secondtubular element 4 does not protrude radially beyond the first tubularelement 3, i.e., (D₁−D₂)/2 ≧E in the case of shearing of the connectingweb 5 across the longitudinal axis 2 by a distance E (FIG. 4). Due tothe fact that the second tubular element 4 does not protrude beyond thefirst tubular element 3 after fixation of the sleeve 1, it is possibleto achieve the result that the instrument used for fixation can beremoved easily from the sleeve 1.

The sleeve 1 shown here has a radial slot 9 between the intermediateends 22; 23 of the tubular elements 3; 4, its depth T being smaller thanthe outside diameter D₂ of the second tubular element 4. The connectingweb 5 is arranged parallel to the longitudinal axis 2 and on the frontfaces 28; 29 orthogonal to the longitudinal axis 2 it is fixedlyconnected to the two tubular elements 3; 4 on the intermediate ends 22;23.

As shown in FIG. 3, the connecting web 5 is designed as a circular ringsegment having a central angle α of approx. 90° in a cross sectionorthogonal to the longitudinal axis 2, where the inside diameter of thecircular ring segment 26 corresponds to the diameter d of the centralbore 8 in the tubular elements 3; 4 and the outside diameter of thecircular ring segment 26 corresponds to the outside diameter D₂ of thesecond tubular element 4. Due to the fact that the connecting web 5 inthe undeformed state borders on the wall 27 of the central bore 8 on theinside (FIG. 3), this yields the result that after shearing of theconnecting web 5 across the longitudinal axis 2 (FIG. 5), the connectingweb protrudes partially into the central bore 8 a in the first tubularelement 3 and forms an axial stop for the wire 10, in particular aKirschner wire. The cross-sectional area q of the connecting web 5embodied as a circular ring segment 26 must be shearable across thelongitudinal axis 2 while also being stable enough to absorb axialforces between the sleeve 1 and the wire 10 (FIG. 5) and to absorbtorques between the two tubular elements 3; 4.

The embodiment of the device depicted in FIGS. 4 and 5 comprises a wirehaving a thread 11 on its distal end 12 and a sleeve 1 which differsfrom the sleeve 1 depicted in FIGS. 1 through 3 only in that the firsttubular element 3 comprises an axial segment 15 having a thread 16. Thesegment 15 may in particular be implemented as a conical segment havinga conical thread 16, whereby the conical thread 16 tapers toward theexterior end 20 of the first tubular element 3. FIG. 4 shows the deviceprior to fixation, so that the sleeve 1 is axially displaceable on thewire 10. In FIG. 5, the device is depicted with the sleeve 1 secured onthe wire 10. Fixation is accomplished by means of an instrument (notshown) by simultaneous shaping, in particular by shearing the wire 10and the sleeve 1 positioned on it in the area of the connecting web 5 byan amount E, measured across the longitudinal axis 2. Due to the factthat the wire 10 and the connecting web 5 are sheared and the centralbores 8 a, 8 b of the two tubular elements 3; 4 are eccentric relativeto one another by the amount E after shearing, this yields an axiallyand rotationally form-fitting fixation of the sleeve 1 on the wire 10.

The surgical technique during implantation of the inventive devicepreferably comprises the following steps:

a) screwing a wire into the bone to be treated;

b) applying the sleeve to the wire, in particular a Kirschner wire,optionally by means of a suitable instrument;

c) pushing the instrument onto the sleeve on the wire;

d) correct positioning of the instrument;

e) applying an optimal axial prestress between the wire and the sleeveand thus to the bone fragments to be treated;

f) fixation of the sleeve on the wire;

g) optionally severing the wire on the proximal end of the sleeve; and

h) removing the instrument.

1-15. (canceled)
 16. A sleeve for attachment to an end of a bonefixation element comprising: first and second tubular elements sharing acommon central longitudinal axis, each of the first and second tubularelements having a central bore with a diameter D, an exterior end, andan intermediate end with a front face having a surface area orthogonalto the central longitudinal axis; and a shearable connecting web axiallyconnecting the two tubular elements to one another, wherein the firsttubular element and second tubular element are configured and adapted tobe axially secured to a bone fixation element inserted within thecentral bore by at least partially shearing the connecting web.
 17. Thesleeve of claim 1, wherein the connecting web is parallel to the centrallongitudinal axis between the front faces on the intermediate ends ofthe first and second tubular elements.
 18. The sleeve of claim 1,wherein the connecting web has a cross-sectional area that is orthogonalto the central longitudinal axis.
 19. The sleeve of claim 18, whereinthe cross-sectional area of the connecting web is shaped as a circularring segment having a central angle α between 5° and 350°.
 20. Thesleeve of claim 16, wherein each of the first and second tubularelements includes an outer lateral surface extending parallel to thecentral longitudinal axis.
 21. The sleeve of claim 16, wherein thesecond tubular element has a cross-sectional area Q orthogonal to thecentral longitudinal axis on its intermediate end, and the connectingweb has a cross-sectional area q orthogonal to the central longitudinalaxis, where the ratio q/Q is between about 0.05 and 0.95.
 22. The sleeveof claim 16, wherein the connecting web has a cross sectional area qorthogonal to the central longitudinal axis, where q is between 0.05 mm²and 40 mm².
 23. The sleeve of claim 16, wherein the connecting web has across sectional area q orthogonal to the central longitudinal axis witha width b and a height h, where the ratio h/b is between 0.1 and
 1. 24.The sleeve of claim 16, wherein the first and second tubular elementsand the connecting web are formed as a single, monolithic unit.
 25. Thesleeve of claim 16, wherein the first and second tubular elements havefirst and second outside diameters, and the sleeve further comprises aradial slot between the first and second tubular elements, the slothaving a radial depth T less than the outside diameters of the first andsecond tubular elements.
 26. The sleeve according to claim 16, whereinthe first and second tubular elements are metallic.
 27. The sleeve ofclaim 26, wherein the first and second tubular elements are formed ofsteel, steel alloy, titanium, or titanium alloy.
 28. The sleeve of claim16, wherein the first tubular element has an outside diameter D₁ and thesecond tubular element has an outside diameter D₂ such that D₂<D₁. 29.The sleeve of claim 16, wherein the first tubular element includes athreaded portion on its exterior end.
 30. The sleeve of claim 29,wherein the threaded portion is conical.
 31. The sleeve of claim 16,wherein at least a portion of the connecting web is configured anddimensioned to project into the central bore upon partial shearing ofthe connecting web.
 32. A bone fixation device comprising: alongitudinal bone fixation element having at least a first endconfigured to engage bone and a second end; and a sleeve for attachmentto the second end of the bone fixation element, the sleeve includingfirst and second tubular elements sharing a common central longitudinalaxis, each of the first and second tubular elements having a centralbore with a diameter D, an exterior end, and an intermediate end with afront face having a surface area orthogonal to the central longitudinalaxis, and a shearable connecting web axially connecting the two tubularelements to one another, wherein the sleeve is axially secured to thebone fixation element by at least partially shearing the connecting weband the bone fixation element.
 33. The device of claim 32, wherein thefirst tubular element includes a threaded portion on its exterior end.34. A bone fixation method comprising: inserting a longitudinal bonefixation element into a bone, the bone fixation element having at leasta first end configured to engage bone and a second end; placing a sleeveover the second end of the bone fixation element, the sleeve includingfirst and second tubular elements sharing a common central longitudinalaxis, each of the first and second tubular elements having a centralbore with a diameter D, an exterior end, and an intermediate end with afront face having a surface area orthogonal to the central longitudinalaxis, and a shearable connecting web axially connecting the two tubularelements to one another, and shearing at least a portion of theconnecting web and the bone fixation element to axially secure thesleeve to the bone fixation element.
 35. The method of claim 32, furthercomprising severing at least a portion of the bone fixation element nearthe second end of the bone fixation element.